The roofing industry has long utilized a variety of roofing kettles for heating roofing material for application to a roof. Such kettles are used primarily in large commercial roofing jobs where large expanses of flat roof are to be covered with liquid asphalt as part of the roofing process. The liquid asphalt is one element of a layering of materials applied to the roof to form a water tight built up roof. The asphalt is heated in the kettle to bring it from a solid form to the desired liquid consistency for application to the roof.
A common feature of all roofing kettles is that they heat the asphalt to a temperature around 450 degrees F. It is at this temperature that the liquid asphalt contains sufficient heat to be pumped by the kettle pump to the roof surface, and subsequently transported by other devices across the roof to the areas where it is dispensed and mopped onto the roof. During such processes, the liquid asphalt loses heat. If the heat losses are too large, the liquid asphalt loses its bonding capability. To avoid this problem, roofers have traditionally heated the liquid asphalt to a relatively high temperature to compensate for cool down during the roofing application. Traditionally the temperatures maintained in the roofing kettles have been within 150 degrees of the temperature at which volatile gases are cooked off the asphalt. Such gases can be very dangerous if they are trapped within the kettle and mixed with a suitable oxygen supply such that a flash fire, or explosion occurs in or about the kettle when an ignition source is present. This has resulted in a tradition of hazardous kettle operation where any number of operating circumstance may lead to asphalt overheating and subsequent asphalt fires and explosions. Unfortunately, many roofing workers have suffered very severe burns, and even death, from such kettle overheating.
Up until the creation of the present invention, no kettles were available which provided overall automated electronic control of kettle ignition and operating temperature. To maintain the kettle at a desired temperature, the kettle operator continually manipulated fuel supply valves to increase and decrease the amount of fuel being burned in response to visual reading of a temperature gauge. This varied the kettle temperature, and, if the kettle were not carefully monitored, frequently lead to kettle overheating and fires. This process was also imprecise and labor intensive. In addition, some electrical shut off systems are presently employed which would totally cut off the supply of fuel to the kettle if it became overheated. However, such system, while providing this additional safety feature, would then have to be manually reignited by the roofers using ignition wands. In addition such systems still left for manual control and manipulation the specific temperature control for the kettle. Thus, while the kettles had the advantage of the shut off safety feature once a dangerous temperature is reached, they still require moment by moment monitoring and gas supply control to maintain a consistent and safe kettle temperature. As a result, a very labor intensive, and highly variable operation has had to be employed in the operation of the thousands of roofing kettles in use today.